The present disclosure relates to process variable transmitters. In particular, the present disclosure relates to process variable transmitters with wireless transceivers.
In processing plants, gases and liquids are routed through various conduits and tanks. In order to control the operation of a plant, the current status of the liquids and gases in the various portions of the plant as well as the state of controlled devices such as valves and burners must be monitored. The variables monitored to determine these states are referred to generally as process variables and can include flow rates, pressures, differential pressures, temperatures, tank levels, valve positions, and the like. These process variables are provided to a control room by field devices known as process variable transmitters. Each process variable transmitter includes a transmitter housing that encases at least one circuitry module used to determine a value for a process variable. The circuitry module determines the value for the process variable based on one or more sensor signals it receives from one or more process variable sensors that are measuring a state of the process fluid or a controlled device. The circuitry module also transmits the value of the process variable to a control room using either wireless communication or wired communication. In some cases, the circuitry module transmits the process variable using a two-wire process control loop which is also used to power the process variable transmitter.
One type of wireless communication system that has been used in the past is a specialized wireless communication standard designed to allow process transmitters to communicate with specialized gateways or specialized handheld devices that are not used outside of the process control industry. These systems minimize power consumption such that the wireless communication module can be powered from a battery or other local source or from the two-wire process control loop without impacting the performance of the process variable transmitters connected to the process control loop. Examples of such wireless communication modules include modules that use the WirelessHART® communication standard and that can be mounted within the transmitter housing or can be installed in a port on the housing. Another example system is shown in U.S. Patent Publication 2010/0145476.